tcthome Loc: NJ

I seen a show on this once. If you can catch your subject & put it in a cooler for a while , get set up, then place your subject on a plant(eg.) or what ever. gives you time to do your thing.
Also , sometimes close up photography can be better & maybe more of what you had in mind.

bleirer

I think I'm with userID on this one. Magnification is independent of sensor size. It is just cropping, which was already discussed.

User ID

Your first sentence is our only point of disagreement. Study optics ? You have no idea who you’re talking to. My point is that your first sentence is only true when isolated from any actual output. Such technical facts have no effect on results, true facts though they be.

If you reduce image magnification on the sensor, you satisfy your technical facts but when you actually output that reduced magnification image you wind up cranking the lost magnification back in. IOW any reduction of magnification at the sensor gains you no actual DoF in your output. A technical gain at the sensor level is no gain at all if it must be nullified to get equivalent output magnification. What happens before final output is merely meaningless tech chatter. It can be true, yet meaningless. If you wanna dwell on useless truth, ok for you ... but it provides no good advice for actual practice.

RWR Loc: La Mesa, CA

I assumed that you merely misspoke, and would correct it yourself.

petrochemist Loc: UK

Long bellows aren't needed if you're using shorter focal lengths. The wide angle bag bellows could be long enough to fill the 5x4 frame with a housefly through my microfische lens (17mm focal length) The subject would need a LOT of light to enable focusing and yes DOF wouldn't be enough.

User ID

Slit lighting, plus a lab jack for the subject, will get you the DoF. Same principle as the scanning electron microscope, but using photons, not electrons. No cryogenics needed.

fetzler Loc: North West PA

Do you really have a 17mm lens that has 4 x5 inch coverage? I can think of many mechanical issues associated with using a lens of this focal length on a view camera. Such a lens would have a 35mm equivalent of about 6mm. I think even 35mm fish-eye lenses have focal lengths longer than 6mm

My overall point was that more magnification is required to fill the frame of a 4 x 5 in negative than for a micro 4/3 sensor. Because the smaller sensor requires less magnification it will have more DOF given all other factors are the same. Of course you can crop a full frame sensor you just need to consider the final number of pixels in the cropped image.

petrochemist Loc: UK

It won't even cover 35mm at infinity focus, but if you're doing macro the image diameter increases with the magnification.

Smaller sensors need more magnification to produce the final print, this makes it more important that the image on the sensor is sharp. If the sensor image is only as sharp as a FF image needs to be to JUST look focused then the final output will look blured.

User ID

You’ll hafta mount a mess of LEDs right onto the lens board as there isn’t enough clearance for separate lights to shine on the subject. A conical snoot between the board and the lens would resolve that issue reasonably well.

imagemeister Loc: mid east Florida

I have used a 50% pellical mirror mounted in front of the lens @ 45 degrees for directing coaxial light to the subject for 10:1 enlargement - lens to subject being around 40mm using a Zeiss 100mm macro in reverse on a special 8X10 bellows camera - the subject being large scale integrated circuits.
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User ID

15X with a 17mm lens would not allow clearance for your device, which acoarst would be very useful in various more typical macro photo situations.

LWW Loc: Banana Republic of America

They are referring to using different focal lengths.

If I use a 1:2 lens and have something in focus, cropping it will not change that.

bdk Loc: Sanibel Fl.

just as bad....

E.L.. Shapiro Loc: Ottawa, Ontario Canada

Trying to calculate the depth of field mathematically is difficult when workg in the field. You can go into all the physical and optical theory and still not solve certain issues.

Re: extensions tubes vs. Macro lenses, this is what I have found in practical working conditions while shooting small objects- close up.

I advise you to continue using your macro lens, rather than using a standard lens with an extension tube to enable closer focusing. When you use an extension tube, in some case you may get vignetting. Macro lenses are formulated for closeup work and perform best at very close distances.

The depth of field is governed by focal length, distance and aperture. How you enable the lens to focus closer than its minimum focusing distance is not a factor.

The use of an extension tube also varies the effective aperture with extension tubes. Thereis a loss of light that will require a slower shutter speed of a high IOS setting to compensate if you want to maintain a particular f/stop.

If you do extensive macro work that requires an increased depth of field you may want to consider purchasing a TILT/SHIFT macro lens. This type of lenses allows you to employ the Scheimpflug principle whereby you can use wider apertures to avoid diffraction and still achieve greater depth of field in certain situations.

Winslowe

Depth of field is determined by aperture and magnification. Focal length and distance play no part.